In October 2020, the world was still reeling from the COVID-19 pandemic. The more contagious delta strain was spreading, and fear was ever-present.

Positive news from vaccine trials offered some hope that illness and death would be reduced and that the world would soon return to normal.

By 2022, the pandemic had subsided, but normal did not return as Russia launched a full-scale invasion of Ukraine, igniting the bloodiest war in Europe since the end of World War II in 1945.

A series of surprise attacks on Israel by Hamas terrorists in the Gaza Strip on Oct. 7 started a second major war that, as of this writing, threatens to spread beyond Israel and Gaza.

Iran has already threatened to retaliate against Israel for bombing Hamas facilities in Gaza.

So, as 2023 draws to a close, the world faces instability that threatens to spread to other regions.

China has made it clear that it wants to take over Taiwan and is prepared to use military force if necessary.

North Korea remains focused on developing its nuclear and ballistic missile capabilities.

Meanwhile, rising low-level conflicts elsewhere threaten to destabilize a number of key nations.

For South Korea, the immediate and important question is whether its ally, the United States, can live up to its security commitments.

The current alliance between South Korea and the United States requires both parties to respond to any military attack on the other.

In practice, this has justified the continued presence of US forces in South Korea.

At present, no one doubts the US commitment to help defend South Korea, but its ability to do so may be limited.

Concerns about US capability prompted Treasury Secretary Janet Yellen to make a statement that the US can fund support for Ukraine and Israel at the same time.

The US commitment to Ukraine and Israel is strong, but increasingly troubled by domestic politics.

Under the influence of former President Donald Trump’s MAGA ideology, Republicans have become increasingly critical of support for Ukraine.

Similarly, left-leaning progressive Democrats have become increasingly critical of Israel’s policies toward the Palestinians and have called for restraint.

US President Joe Biden and politicians from both parties have taken an increasingly hawkish stance toward China on trade and security issues.

The US has long maintained strategic ambiguity about what it would do if China invaded Taiwan, but the mood in Washington has become more hawkish as relations with China have deteriorated.

This suggests that the US would actively support Taiwan, further straining its military resources.

The US remains the world’s preeminent military power. Its military budget is by far the largest in the world and, as a percentage of gross domestic product, is larger than that of its European allies, Japan, or South Korea.

Like other parts of the budget, however, it is financed by taxes and borrowing. In 2022, the federal debt will be 129 percent of GDP, the highest level since 1945, the last year of World War II. This figure is nearly double the long-term average of 65 percent of GDP.

Then there are the demographic concerns. The US military is already having trouble recruiting volunteers, but a decline in the birthrate in the late 2000s will soon make it even harder to find recruits.

A military draft would immediately increase the number of soldiers, but such a move would be politically unpopular.

Finally, there is the question of public support for US military intervention abroad. Long-standing alliances, such as NATO and the alliances with South Korea and Japan, continue to enjoy strong public support.

Much of this is because generations of leaders from both parties have defined these nations as allies and supported the alliances.

Since World War II, however, US public support for foreign wars has begun to erode as they have dragged on.

The steady erosion of support has led the US to negotiate an end to the war and then withdraw.

The same pattern is repeating itself as support for Ukraine has waned this year.

Russia, Iran, China, and terrorist organizations like Hamas no doubt see US weakness and are willing to exploit it.

But each is much weaker than the US, and together they are much weaker than the US and its allies.

To make this point, and to deter future wars, the US and its allies must present a united front while building public will at home.